1. Field of the Invention
The present invention relates to the design of linear integrated circuits; and, in particular relates to the design of linear integrated circuits for audio applications, such as audio amplifiers.
2. Discussion of the Related Art
In an audio output circuit, an 8-ohm speaker is typically driven by a pair of power amplifiers in a bridge configuration. FIG. 1 shows such a configuration in a monophonic output circuit 100 of an audio system.
As shown in FIG. 1, signal 104 is amplified by gain amplifier 101. The output signal of gain amplifier 101 is then amplified by amplifiers 108 and 109 provided in a bridge configuration to drive an 8-ohm speaker 102. Note that the reference voltage on node 110 is voltage between a power supply V.sub.dd and a power supply V.sub.ss.
The output current in each of amplifiers 108 and 109 is provided by two power transistors. FIG. 2 shows a typical output section in an audio output circuit. As shown in FIG. 2, power transistors 201 and 202 are provided to conduct current alternatively from the power supply V.sub.dd to output node 203, and from output node 203 to power supply V.sub.ss. In FIG. 2, power transistors 201 and 202 are controlled respectively by high side control circuit 204 and low side control circuit 205, each receiving an input signal from an amplifier 206. To reduce the current drawn by circuit 100 from the power supply and hence reduce the dissipation of circuit 100, only one of power transistors 201 and 202 should be conducting at any given time. Simultaneous conduction is undesirable.